JP4127151B2 - Start control device for internal combustion engine - Google Patents

Description

  The present invention relates to a start control device for suppressing self-ignition during start of an internal combustion engine.

A technique is known in which ignition control is continued even after a stop operation of an internal combustion engine, and unburnt fuel in a cylinder is completely burned, and then ignition control is stopped to improve exhaust emission performance (Patent Document) 1). In addition, Patent Documents 2 to 4 exist as techniques related to the present invention.
JP-A-5-312083 Japanese Patent Laid-Open No. 2002-4985 JP 2001-173488 A JP-A-10-227236

  In a so-called in-cylinder direct injection engine that directly injects fuel into the cylinder, fuel is likely to adhere to the inner wall surface of the cylinder because fuel injection with a relatively high penetration force is performed. The adhering fuel is vaporized while the engine is stopped, so that a fuel mixture with a high combustible gas concentration may be formed in the cylinder. In particular, when the engine is stopped from a high load operation or the like, the engine is stopped at a high temperature, so that the attached fuel is easily vaporized, and the fuel mixture in the cylinder is likely to reach a flammable concentration. In this way, when the engine is restarted in a state where there is a fuel mixture with a high combustible gas concentration in the cylinder, there is a risk of self-ignition during the compression stroke during cranking. Furthermore, when the engine temperature is high, self-ignition tends to occur. This self-ignition causes abnormal noise, reverse rotation of the crankshaft, etc., and deteriorates startability.

  In addition, self-ignition occurs when the fuel adhering to the intake port is vaporized and flows into the cylinder, so it can be generated not only in an in-cylinder direct injection type engine but also in an engine that injects fuel into the intake port. There is sex.

  However, in the prior art, unburned fuel is burned only when the engine is stopped. Therefore, even when the unburned fuel in the cylinder is made less than the flammable concentration when the engine is stopped, the adhering fuel is vaporized while the engine is stopped, so that the unburned fuel may reach the flammable concentration at the time of restart and cause self-ignition. .

  Accordingly, an object of the present invention is to provide a start control device for an internal combustion engine that suppresses self-ignition that occurs when the internal combustion engine is started.

Startup control apparatus of the present invention, thereby starting the internal combustion engine by performing the ignition means for igniting the fuel mixture in the combustion chamber of the internal combustion engine, a start request means for requesting the starting of the internal combustion engine, the cranking Starting means, determining means for determining the possibility of self-ignition of the internal combustion engine at the time of the start request of the start request means based on the temperature of the internal combustion engine, and possibility that the determining means is capable of self-ignition of the internal combustion engine Is determined to be higher than a predetermined level, the fuel mixture in the combustion chamber is ignited by the ignition means after the start request from the start request means and before cranking is started by the start means. After that, the above-mentioned problem is solved by providing start-up procedure control means for starting up the internal combustion engine by performing cranking by the start-up means (claim 1).

According to startup control apparatus of the present invention, if it is determined that there is a high possibility of self-ignition by determination means ignites the fuel mixture in the combustion chamber before the start of the internal combustion engine, burning a fuel-air mixture Therefore, self-ignition can be suppressed. Further, since the fuel mixture is discharged after combustion, it is possible to prevent the exhaust emission from deteriorating.

Startup control apparatus of the present invention comprises a compression cylinder discrimination means for discriminating first the compression stroke cylinder at the time of starting of the internal combustion engine, the start-up procedure control means, during the starting of the compression cylinder discrimination means has discriminated The fuel mixture in the combustion chamber may be ignited by the ignition means only for the cylinder that is initially in the compression stroke. In this way, by igniting only the cylinder that is initially in the compression stroke at the time of starting, power consumption at the time of ignition can be reduced.

  According to the present invention, since self-ignition that occurs at the time of starting the internal combustion engine can be suppressed, abnormal noise, reverse rotation of the crankshaft, and the like can be prevented, and the startability of the internal combustion engine can be improved.

  FIG. 1 shows a main part of an internal combustion engine to which the start control device of the present invention is applied. The internal combustion engine 1 in FIG. 1 is configured as a cylinder injection type four-cycle gasoline engine, and a plurality of cylinders 3 (only one is shown in FIG. 1) are formed in the cylinder block 2. 3, the piston 4 is inserted so as to be movable up and down. The opening of each cylinder 3 is closed by a cylinder head 5, and a combustion chamber 6 is formed in each cylinder 3 by the wall surface of the cylinder 3, the piston 4 and the cylinder head 5. Each combustion chamber 6 is connected to an intake passage 7 for taking in intake air and an exhaust passage 8 for guiding exhaust from the combustion chamber 6 to a predetermined exhaust position. Each combustion chamber 6 includes an intake valve 9 and an exhaust valve 10 for opening and closing the passages 7 and 8 with respect to the combustion chamber 6, an injector 11 as fuel injection means for injecting fuel into the combustion chamber 6, and a combustion chamber And a spark plug 12 as ignition means for igniting the fuel mixture 6. The reciprocating motion of each piston 4 is transmitted as a rotational motion to the crankshaft 14 via the connecting rod 13.

  The internal combustion engine 1 includes a valve operating mechanism 15 that can arbitrarily change the valve operating characteristics of the valves 9 and 10. The valve mechanism 15 includes cam devices 16 and 17 that open and close the valves 9 and 10, and valve characteristic changing devices 18 and 19 that change the valve characteristics of the valves 9 and 10. The internal combustion engine 1 is provided with a starter 20 as a starter. The starter 20 includes a starter motor 21, a speed reduction mechanism (not shown) that transmits the rotational motion of the starter motor 21 to the crankshaft 14, and a battery (capacitor) 22 that supplies electric power to the starter motor 21.

  The operating state of the internal combustion engine 1 is controlled by an engine control unit (ECU) 23. The ECU 23 is configured as a computer in which a microprocessor and peripheral devices such as ROM and RAM necessary for its operation are combined. The ECU 23 controls the operation of the injector 11 and the spark plug 12, for example, and adjusts the fuel injection timing, the fuel injection amount, and the ignition timing so that the internal combustion engine 1 is properly operated. The ECU 23 controls the valve mechanism 15 according to the operating state of the internal combustion engine 1 to change the valve characteristics of the valves 9 and 10. In order to appropriately control the operation of such various devices in accordance with the operating state of the internal combustion engine 1, for example, a signal corresponding to the coolant temperature of the internal combustion engine 1 output from the water temperature sensor 24 is input to the ECU 23. The These specific controls may be the same as known ones, and details are omitted here.

  The ECU 23 controls the operation of the starter 20 to start the internal combustion engine 1. FIG. 2 is a flowchart showing a control routine executed by the ECU 23 to start the internal combustion engine 1. Further, the ECU 23 monitors the start of the internal combustion engine 1 by a routine different from the routine of FIG. 2. For example, when a predetermined condition is satisfied, for example, the ignition switch (IG) 25 is turned on, the internal combustion engine 1 is A start request for the engine 1 is issued. The control routine of FIG. 2 is executed when this start request is issued. The ECU 23 functions as a start procedure control unit and a start request unit by executing these control routines.

  In the control routine of FIG. 2, the ECU 23 first determines in step S11 whether or not the cooling water temperature of the internal combustion engine 1 is equal to or higher than a predetermined temperature. The coolant temperature has a correlation with the temperature of the internal combustion engine 1. Therefore, when the coolant temperature is high, it can be determined that the internal combustion engine 1 is likely to self-ignite at the time of starting. The ECU 23 functions as a determination unit by executing this process. When it is determined that the coolant temperature is equal to or higher than the predetermined temperature, the process proceeds to step S12, and the ECU 23 operates the spark plug 12 to burn the fuel mixture in the combustion chamber 6. In the next step S13, the ECU 23 operates the starter motor 21 to start the internal combustion engine 1. Thereafter, the current control routine is terminated. If it is determined in step S11 that the cooling water temperature is not equal to or higher than the predetermined temperature, step S12 is skipped.

  FIG. 3 shows an example of temporal changes in combustible gas concentration and gas temperature in the combustion chamber 6 when the control routine of FIG. 2 is executed. When the internal combustion engine 1 is stopped from the high load operation, as is clear from FIG. 3, the combustible gas concentration in the combustion chamber 6 is the concentration that causes the self-ignition of FIG. 3 when the internal combustion engine 1 is stopped (self-ignition concentration). ) In the following, it gradually rises while the internal combustion engine 1 is stopped due to the vaporization of fuel or the like adhering to the wall surface of the cylinder 3, and becomes higher than the self-ignition concentration. Note that the self-ignition concentration is experimentally determined as the concentration at which self-ignition may occur during the compression of the fuel mixture. Further, when the internal combustion engine 1 is stopped in this way, the gas temperature in the combustion chamber 6 (temperature of the internal combustion engine 1) also falls below the temperature (self-ignition temperature) that is likely to cause self-ignition in FIG. It is hard to do. When the start of the internal combustion engine 1 is requested in such a state, the ECU 23 operates the spark plug 12 immediately after the start request, and the fuel mixture in the combustion chamber 6 is combusted. Due to this combustion, the concentration of combustible gas rapidly decreases and becomes lower than the concentration causing self-ignition. This combustion is performed under substantially atmospheric pressure before starting by the starting means. Therefore, reverse rotation of the crankshaft is unlikely to occur. Thereafter, the starter motor 21 is started and cranking of the internal combustion engine 1 is started.

  As described above, by executing the control routine of FIG. 2, when there is a high possibility of self-ignition, the fuel mixture in the combustion chamber 6 is burned by the spark plug 12 before cranking by the starter motor 21. Therefore, self-ignition can be suppressed.

Next, it will be described with reference to FIGS. 4 and 5 another example of a control routine that ECU23 performs. 4 and 5, the same processes as those in FIG. 2 are denoted by the same reference numerals, and description thereof is omitted.

  In the control routine of FIG. 4, self-ignition of the internal combustion engine 1 is suppressed by injecting fuel from the injector 11. The control routine of FIG. 4 is executed when the internal combustion engine 1 is requested to start. In the control routine of FIG. 4, the ECU 23 first determines in step S11 whether or not the coolant temperature is equal to or higher than a predetermined temperature. When it is determined that the temperature is equal to or higher than the predetermined temperature, the process proceeds to step S21, where the ECU 23 operates the injector 11 to inject fuel into the combustion chamber 6. The amount of fuel injected from the injector 11 is adjusted according to the cooling water temperature, for example, by increasing the fuel amount when the cooling water temperature is high. Thereafter, the process proceeds to step S13, and thereafter the same processing as in the control routine of FIG. 2 is performed.

  FIG. 6 shows an example of temporal changes in combustible gas concentration and gas temperature in the combustion chamber 6 when the control routine of FIG. 4 is executed. As can be seen from FIG. 6, the combustible gas concentration in the combustion chamber 6 when the internal combustion engine 1 is stopped from a high load operation or the like is due to the vaporization of the fuel adhering to the cylinder 3 while the internal combustion engine 1 is stopped. It falls within the autoignition concentration range of FIG. Further, the gas temperature in the combustion chamber 6 does not drop below the self-ignition temperature in FIG. When the start of the internal combustion engine 1 is requested in such a state, the ECU 23 operates the injector 11 immediately after the start request and injects fuel into the combustion chamber 6. The injected fuel lowers the gas temperature in the combustion chamber 6 to the auto-ignition temperature or less by the latent heat of vaporization, and enriches the air-fuel ratio of the fuel mixture to raise the combustible gas concentration outside the auto-ignition concentration range. Thereafter, the starter motor 21 is started and cranking of the internal combustion engine 1 is started.

  Therefore, the self-ignition at start-up can also be suppressed by executing the control routine of FIG. Note that the ECU 23 grasps the ignition timing and the like of each cylinder 3 by referring to the angle of the crankshaft 14 during operation of the internal combustion engine 1 as its function, and the ignition timing and the like grasped during operation when the internal combustion engine 1 is stopped. Referring to FIG. 4, it may have a function of discriminating which cylinder is in the compression stroke first at the next start. By discriminating the cylinder in this way, the ECU 23 functions as a compression cylinder discrimination means. In this case, the ECU 23 may perform the process of step S12 in FIG. 2 or the process of step S21 in FIG. 4 only on the spark plug 12 or the injector 11 of the cylinder that is initially in the compression stroke at the time of starting. In this way, by processing only the cylinders that are initially in the compression stroke, the power consumption during ignition and the amount of fuel to be injected can be reduced.

  In the control routine of FIG. 5, the self-ignition of the internal combustion engine 1 is suppressed by changing the closing timing of the intake valve 9. The control routine of FIG. 5 is started simultaneously with the activation of the ECU 23, and is repeatedly executed at a predetermined cycle during the operation of the ECU 23. In the control routine of FIG. 5, the ECU 23 first determines whether or not a request for starting the internal combustion engine 1 has been made in step S31. If it is determined that there is no start request, the current control routine is terminated. If it is determined that the start request has been made, the process proceeds to step S32, where the ECU 23 determines whether the start motor 21 is operating. If it is determined that the starter motor 21 is not operating, the process proceeds to step S11, and the ECU 23 determines whether or not the coolant temperature is equal to or higher than a predetermined temperature. When it is determined that the coolant temperature is equal to or higher than the predetermined temperature, the process proceeds to step S33, and the ECU 23 sets the closing timing of the intake valve 9 to the most retarded angle. The position where the closing timing of the intake valve 9 is retarded is not limited to the most retarded angle. For example, the delay amount of the valve closing timing may be set according to the cooling water temperature, such as retarding the valve closing timing as the cooling water temperature is higher. By delaying the closing timing of the intake valve 9 in this way, the pressure is adjusted so that the pressure in the combustion chamber 6 does not rise above a predetermined pressure that is likely to cause self-ignition during cranking. In subsequent step S13, the ECU 23 operates the starter motor 21. If it is determined in step S11 that the cooling water temperature is not equal to or higher than the predetermined temperature, step S33 is skipped.

  If it is determined in step S32 that the starter motor 21 is operating, the process proceeds to step S34, where the ECU 23 has passed the first minimum value (first minimum value) after the voltage of the battery 22 has been started. Determine whether or not. FIG. 7 shows an example of the change over time of the voltage of the battery 22 when the internal combustion engine 1 is started. As apparent from FIG. 7, the voltage of the battery 22 does not increase until the cylinder 3 (first compression cylinder) that is initially in the compression stroke at the start passes the position of the top dead center for the first time. Therefore, whether or not the first compression cylinder has first passed top dead center is determined by monitoring the voltage change rate ΔV (the slope of the voltage change) of the battery 22 during Δt after the operation of the starter motor 21. be able to. For example, when ΔV becomes larger than 0 (the voltage has passed the first minimum value), it can be determined that the first compression stroke of the internal combustion engine 1 has ended and the first combustion has been performed. By monitoring the voltage of the battery 22 in this way, the ECU 23 functions as a detection unit. If it is determined in step S34 that the first minimum value has not been passed, the current control routine is terminated. On the other hand, if it is determined that the first minimum value has been passed, the process proceeds to step S35, where the ECU 23 advances the valve closing timing of the intake valve 9. Thereafter, the current control routine is terminated.

  Thus, the self-ignition of the internal combustion engine 1 can also be suppressed by changing the valve closing timing of the intake valve 9 to suppress the increase in the pressure in the combustion chamber at the start. Further, since the closing timing of the intake valve 9 is advanced after the detection of the first combustion, it is possible to suppress deterioration of startability due to delaying the closing timing in a short time. The pressure adjustment of the combustion chamber 6 is not limited to adjustment by changing the closing timing of the intake valve 9. For example, the valve characteristics such as the lift amount of the intake valve 9 other than the valve closing timing may be changed and adjusted, or the valve characteristics of the exhaust valve 10 may be changed and adjusted. Further, whether or not the first compression cylinder has passed the top dead center is not limited to the detection based on the voltage change of the battery 22, and is detected by monitoring the torque change of the internal combustion engine 1 or the pressure change in the combustion chamber 6, for example. May be.

  The start control device of the present invention is an internal combustion engine of a so-called hybrid vehicle in which a motor generator functioning as an electric motor and a generator and an internal combustion engine are mounted as power sources, or the internal combustion engine temporarily when a predetermined condition is satisfied. The present invention can also be applied when the internal combustion engine is restarted in an internal combustion engine that performs so-called idling stop. In such an internal combustion engine, the possibility of self-ignition at the time of restart can be determined from the time when the internal combustion engine is temporarily stopped.

  FIG. 8 is a flowchart showing an example of a control routine executed by the ECU 23 to restart such an internal combustion engine. The routine of FIG. 8 is started when the ECU 23 is activated, and is repeatedly executed at a predetermined cycle during the operation of the ECU 23. In FIG. 8, the same processes as those in FIG. 2 are denoted by the same reference numerals, and description thereof is omitted.

  In the control routine of FIG. 8, the ECU 23 first determines in step S41 whether or not the internal combustion engine 1 is stopped. If it is determined that the vehicle is not stopped, the current control routine is terminated. If it is determined that the engine is stopped, the process proceeds to step S42, and the ECU 23 determines whether or not there is a request for restarting the internal combustion engine 1. The restart request is generated when the internal combustion engine 1 is temporarily stopped, for example, when an accelerator pedal or a clutch pedal is depressed or a transmission is operated. If it is determined that there is no restart request, the current control routine is terminated. If it is determined that a restart request has been made, the process proceeds to step S43, and it is determined whether or not a predetermined time has elapsed since the internal combustion engine 1 was stopped. For example, the predetermined time is set to a time when the fuel adhering to the wall surface of the cylinder 3 is vaporized and the combustible gas concentration in the combustion chamber 6 becomes equal to or higher than the self-ignition concentration. If it is determined that the predetermined time has elapsed, the process proceeds to step S12, the spark plug 12 is operated, and the fuel mixture in the combustion chamber 6 is combusted. In subsequent step S13, the ECU 23 operates the starter motor 21 to start the internal combustion engine 1. Thereafter, the current control routine is terminated. If it is determined in step S43 that the predetermined time has not elapsed, step S12 is skipped.

  By executing the control routine of FIG. 8 in this way, it is possible to suppress self-ignition when the internal combustion engine 1 is temporarily stopped and then restarted. In addition, although the ignition plug 12 was used in FIG. 8, you may suppress self-ignition using the injector 11 and the valves 9 and 10. FIG. In such an internal combustion engine, since the internal combustion engine is frequently stopped and restarted, the start control device of the present invention is preferably applied.

  The present invention is not limited to the above-described embodiments, and may be implemented in various forms. The internal combustion engine is not limited to a direct injection internal combustion engine, but can be applied to a port injection internal combustion engine that injects fuel into an intake port. The starting means is not limited to a starting motor, and for example, a method of starting an internal combustion engine by causing combustion in a cylinder in an expansion stroke at the time of starting can be applied.

The means for acquiring the temperature of the internal combustion engine for determining the possibility of self-ignition is not limited to the cooling water temperature. For example, the temperature of the internal combustion engine may be acquired from the temperature of the lubricating oil of the internal combustion engine or the intake air temperature .

The figure which shows the principal part of the internal combustion engine to which the starting control apparatus of this invention is applied. The figure which shows the 1st control routine which ECU of FIG. 1 performs in order to control starting of an internal combustion engine. The figure which shows an example of the time change of the combustible gas concentration and temperature in a combustion chamber at the time of performing the control routine of FIG. The figure which shows the 2nd control routine which ECU of FIG. 1 performs in order to control starting of an internal combustion engine. The figure which shows the 3rd control routine which ECU of FIG. 1 performs in order to control starting of an internal combustion engine. The figure which shows an example of the time change of the combustible gas concentration and temperature in a combustion chamber at the time of performing the control routine of FIG. The figure which shows an example of the time change of the battery voltage at the time of start-up of an internal combustion engine. The figure which shows the control routine which ECU23 performs at the time of restart of the internal combustion engine which stops an engine temporarily when predetermined conditions are satisfy | filled.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 3 Cylinder 6 Combustion chamber 9 Intake valve 10 Exhaust valve 11 Injector (fuel injection means)
12 Spark plug (ignition means)
15 Valve operating mechanism 20 Starter (starting means)
21 starting motor 22 battery (capacitor)
23 Engine control unit (start request means, determination means, start procedure control means, compression cylinder determination means, detection means)

Claims (2)

Ignition means for igniting a fuel mixture in a combustion chamber of the internal combustion engine, start request means for requesting start of the internal combustion engine, start means for starting the internal combustion engine by performing cranking, and a start request means Determination means for determining the possibility of self-ignition of the internal combustion engine at the time of a start request based on the temperature of the internal combustion engine, and the determination means determines that the possibility of self-ignition of the internal combustion engine is higher than a predetermined level In this case, the fuel mixture in the combustion chamber is ignited by the ignition means after the start request from the start request means and before the cranking is started by the start means, and then the start means An internal combustion engine start control device comprising start procedure control means for starting the internal combustion engine by performing cranking .   Compression cylinder discrimination means for discriminating a cylinder that first becomes a compression stroke at the start of the internal combustion engine, the start procedure control means for the cylinder that becomes the compression stroke first at the time of startup determined by the compression cylinder discrimination means; 2. The start control device for an internal combustion engine according to claim 1, wherein the fuel mixture in the combustion chamber is ignited by the ignition means only.

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